Method for debarking in a drum, and separation of bark from a log flow

Abstract

The invention relates to a continuously operating drum debarking method for processing logs. The logs to be de-barked into a debarking drum ( 4 ′) having no bark discharge openings in the shell. The logs together with the bark loosened therefrom are discharged to a downstream bark separating system. Therein, the logs are subjected mutual movements resulting in the removal of bark from about the logs. The thus separated bark pieces are further discharged onto a conveyor system located under the separating equipment.

1 . A debarking method for logs, the method comprising an essentially continuously operating debarking process, wherein the logs to be debarked are fed into a cylindrical debarking drum ( 4 ′) having a drum shell, an open inlet end, an opposite essentially open discharge end and a longitudinal essentially horizontal central axis, the debarking drum is rotated around the central axis, the logs and their loosened bark are discharged from the debarking drum to a conveyor system, the logs are subjected to a mutual movements on said conveyor system in order to separate the loosened bark and the logs, wherein bark is loosened from the logs in a debarking drum ( 4 ′) having no bark discharge openings in the drum shell.  
     
     
         2 . The method of  claim 1 , wherein a roller conveyor ( 9 ′) is used in said conveyor system.  
     
     
         3 . The method of  claim 1  wherein is used a debarking drum equipped with an outlet gate ( 43 ) at the discharge end.  
     
     
         4 . The method of  claim 1  for logs to be chipped, wherein the amount of wood being fed into the debarking drum is measured using sensor means for detecting prior to the inlet of the debarking drum the quantity level ( 43 ) and speed of wood traveling to the inlet of debarking drum, while the efficiency of the debarking process is monitored by way of measuring ( 45 ,  46 ,  47 ) the amount of wood being fed into the chipper or the bark content of chips or/and the wood content of removed bark.  
     
     
         5 . The method of  claim 2  wherein the debarking drum is equipped with an outlet gate ( 43 ) at the discharge end and the debarking and bark separation process according to the invention is controlled by adjusting at least one of the variable, the drum feed, the rotating speed of the debarking drum ( 4 ′), the position of the drum gate ( 43 ) and the rotating speed or direction of the rollers ( 48 ) of the roller conveyor ( 9 ′).  
     
     
         6 . The debarking method of  claim 5 , wherein the method uses a roller conveyor comprising a leading section ( 34 ) for separating bark fines and a trailing section ( 35 ) for separating coarser pieces of bark and wood clumps, and that the fall-through discharge fraction of the trailing section is passed to classification and further processing.  
     
     
         7 . A drum debarking apparatus for logs to be chipped, the apparatus comprising a drum feed conveyor ( 41 ′), a debarking drum ( 4 ′) and a roller conveyor ( 9 ′) for transferring debarked logs, characterized in that wherein said debarking drum ( 4 ′) has no bark discharge openings in the shell for removing loose bark from the drum and that said roller conveyor ( 9 ′) is equipped with rollers capable of vigorously moving logs in a lateral direction.  
     
     
         8 . The debarking apparatus of  claim 7 , characterized in that wherein said roller conveyor is equipped with a high-pressure jet washer ( 13 ′).  
     
     
         9 . The debarking apparatus of  claim 7 , wherein a number of the rollers of said roller conveyor ( 9 ′) are equipped with a separate control of their rotating speed and/or direction.  
     
     
         10 . The debarking apparatus of  claim 7 , wherein said roller conveyor ( 9 ′) comprises a narrower-gap leading section ( 34 ) and wider-gap trailing section ( 35 ).  
     
     
         11 . The debarking apparatus of  claim 7 , wherein the debarking drum shell at its inlet end is provided with discharge openings ( 31 ) for removal of sand and small rocks, and downstream from said openings with an internal annular stop ring ( 32 ) for collecting the same.  
     
     
         12 . The debarking apparatus of  claim 7 , wherein the apparatus is equipped with sensor means for detecting the travel speed and quantity level of wood on the drum feed conveyor, as well as with sensor means for detecting the bark content of debarked logs, of chips produced from the logs and/or detecting the wood content of removed bark.  
     
     
         13 . The debarking method of  claim 2 , wherein the method uses a roller conveyor comprising a leading section ( 34 ) for separating bark fines and a trailing section ( 35 ) for separating coarser pieces of bark and wood clumps, and that the fall-through discharge fraction of the trailing section is passed to classification and further processing.  
     
     
         14 . The debarking apparatus of  claim 8 , wherein the apparatus is equipped with sensor means for detecting the travel speed and quantity level of wood on the drum feed conveyor, as well as with sensor means for detecting the bark content of debarked logs, of chips produced from the logs and/or detecting the wood content of removed bark.  
     
     
         15 . The debarking apparatus of  claim 9 , wherein the apparatus is equipped with sensor means for detecting the travel speed and quantity level of wood on the drum feed conveyor, as well as with sensor means for detecting the bark content of debarked logs, of chips produced from the logs and/or detecting the wood content of removed bark.  
     
     
         16 . The debarking apparatus of  claim 10 , wherein the apparatus is equipped with sensor means for detecting the travel speed and quantity level of wood on the drum feed conveyor, as well as with sensor means for detecting the bark content of debarked logs, of chips produced from the logs and/or detecting the wood content of removed bark.